1. Field of the Invention
The present invention generally relates to optical plates, and more particularly to an optical plate for use in, for example, a liquid crystal display (LCD).
2. Discussion of the Related Art
FIG. 7 is an exploded, side cross-sectional view of a typical liquid crystal display device 100 employing a typical prism sheet 10. The liquid crystal display device 100 includes a housing 11 and a plurality of lamps 12 disposed in the housing 11. The liquid crystal display device 100 further includes a light diffusion plate 13, a prism sheet 10, an upper light diffusion film 14 and a LCD panel 15 stacked on the housing 11 in that order. The lamps 12 emit light, and inner walls of the housing 11 are configured for reflecting light upwards. The light diffusion plate 13 includes a plurality of embedded light dispersion particles. The dispersion particles are configured for scattering light, thus enhancing the uniformity of light exiting the light diffusion plate 13.
Referring to FIG. 8, the prism sheet 10 includes a plurality of V-shaped structures 102 on a top surface 101. The V-shaped structure 102 extends along a straight line from one end to another end of the prism sheet 10. A plurality of V-shaped structures 102 are regularly and periodically arranged parallel to each other. The V-shaped structures 102 are configured for collimating light to a certain extent.
In use, light from the lamps 12 enters the light diffusion plate 13 and becomes scattered. Thus, scattered light leaves the light diffusion plate to the prism sheet. The scattered light then travels through the prism sheet before being refracted out at the prism lenses of the prism sheet. Thus, refracted light leaving the prism sheet is concentrated by the prism lenses and increases the brightness (increases illumination) of the prism sheet. The refracted light then propagates into an LCD panel (not shown) disposed above the prism sheet 10. However, moiré interference tends to occur on the LCD panel 15 because the V-shaped structures 102 are aligned similarly to the LCD pixels. In order to decrease the moiré interference, the liquid crystal display device 100 needs to add an upper light diffusion film 14 between the prism sheet 10 and the LCD panel 15. Although the upper light diffusion film 14 is disposed on the prism sheet 10, a plurality of air pockets still exists at the boundary between them. When the liquid crystal display device 100 is in use, light passes through the air pockets, and some of the light undergoes total reflection at one or another of the corresponding boundary. In addition, a great amount of light is absorbed by the upper light diffusion film 14. As a result, a light brightness of the liquid crystal display device 100 is reduced. Moreover, the diffusion plate 13 and the prism sheet 10 are made respectively, therefore air pockets at the boundary between them decreases an efficiency of light utilization.
What is needed, therefore, is a new optical plate and a liquid crystal display using the optical plate that can overcome the above-mentioned shortcomings.